Standard cell preparations for cytological evaluation have, in the past, been produced by spreading or smearing a swab collection of cells across a microscope slide surface and allowing the cells to dry. This procedure often produces a preparation that contains unreadable areas of cells due to contaminates, distorted morphology, folding of the cells, and the overlapping of the cells.
Other methods of depositing cell onto microscope slides include centrifugation of cells onto slide, and hematology smearing.
An attempt to overcome the above described difficulties was made with the apparatus described in U.S. Pat. No. 4,688,513 to Eberle. In general, Eberle teaches a centrifugal chamber for coating slides with a sedimentation product. The apparatus includes a cylindrical sample chamber with a microscope slide abutting one end of the sample chamber. The microscope slide is mounted on a flat surface of a carrier plate which carrier plate is removably connected with the chamber-microscope slide assembly. The mechanism for locking the chamber to the carrier plate is a linearly-displaceable locking slide which is permanently attached to the carrier plate. Alternately, the chamber can be connected to the carrier plate via rotatable disk-like locking mechanism which also is permanently attached to the carrier plate. The sample fluid containing the cells to be analyzed is placed in the chamber and the apparatus then is placed in a centrifuge. After centifuging, the supernatant is removed and then the cylindrical chamber is removed from the assembly. The microscope slide, with the centifuged cells adhered thereto, is removed and the cells then are stained using conventional methodology.
A main disadvantage of the apparatus according to the Eberle patent is that it produces cell collections which contain overlapping cells, cells which have folded over onto themselves during centrifugation, and cells which have a distorted morphology as a result of the centrifugal force.
Another disadvantage of the Eberle device is that the slides must be removed from the assembly in order for the cells to be stained using standard staining methods. With standard Pap-staining techniques, a plurality of the prepared slides containing the cell collections are all immersed into a vessel containing the stain solution. Because slides from different patients are usually near one another in the stain solution, there is a risk that some cells from one patient's slide may become dislodged and float over to and adhere to a different patient's slide. Such "floaters" can generate false-positive results if the floater cell is abnormal and adhere's to a slide containing only normal cells. To overcome the obvious disadvantages of such a procedure, it is important to ensure that the cell collections are isolated from other specimen slides.